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Visitor usolar
Visitor
590 Views
Registered: ‎10-12-2018

Logical operation problem

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Hi All!


I'm new in vhdl programming. I just started tutorial trainings and got some problem.


I'm using ISE 14.7 version. Development board Waveshare DVK601, Core3S250E.
It was programmed simple AND logical operation between two inputs.

For example y<=i0 and i1; Simulation has done and worked how should be.


After flashing the Core, it works like OR logical operation. Then I tested back and found that OR operation works like AND operation.

 

Did anybody had such a problem? Maybe I missed something?

 

Thanks in advance

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Scholar u4223374
Scholar
560 Views
Registered: ‎04-26-2015

Re: Logical operation problem

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I would guess that your inputs and outputs are inverted.

 

For inputs this is achieved by having switches that float high, but pressing the switch pulls them down to ground. Pressing the switch gets a zero, releasing it gets a one.

 

For outputs, it's because the LED anode is connected to 3.3V through a resistor and the LED cathode is connected to the FPGA pin. Setting the pin to 1 (3.3V) means there's no voltage across the LED and therefore no light; setting the pin to 0 (0V) means that the LED turns on.

 

Inverting all inputs and the output of an OR gate turns it into an AND gate, and vice versa.

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Scholar u4223374
Scholar
561 Views
Registered: ‎04-26-2015

Re: Logical operation problem

Jump to solution

I would guess that your inputs and outputs are inverted.

 

For inputs this is achieved by having switches that float high, but pressing the switch pulls them down to ground. Pressing the switch gets a zero, releasing it gets a one.

 

For outputs, it's because the LED anode is connected to 3.3V through a resistor and the LED cathode is connected to the FPGA pin. Setting the pin to 1 (3.3V) means there's no voltage across the LED and therefore no light; setting the pin to 0 (0V) means that the LED turns on.

 

Inverting all inputs and the output of an OR gate turns it into an AND gate, and vice versa.

Visitor usolar
Visitor
531 Views
Registered: ‎10-12-2018

Re: Logical operation problem

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Ah!
Problem solved. I stucked at one point only, but should check the my board schematics.
Thank you, u4223374.
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